3 Karmas which should never be abandoned

Reference - Bhagvadgita
Quoted by - Lord Krishna

Below 3 karmas should never be abandoned till eternity or immortality lasts

1) Yagya
     eg - Japyagya, Gyanyagya, Dravyayagya

2) Tap
      Eg Maun vrat, ekadashi vrat and other fasts and vrats

3) Daan - Act of giving
     Eg - Donations of wealth, food, water etc.

Advantage of Yagya
1) Empowers and pleases heavenly gods
2) Annihilates negative energy
3) Weakens grip of negative powers, demons etc on our command giving section - means a person gets less or zero tendency to steal, exploit etc sins

Any valid example successfully used
Saibaba used to keep dhuni ON always. The fire was never vanished.  And He used to become tense if fire was on brink of vanishing. And He used to make hard efforts so that fire does not get extinguished.

In other examples, all Hindus or Aryas light an oil wick as the Havishya generated from Dravyayagya empowers gods and keeps our spirits clean and away from negative energies, despair, lust, greed, jealousy etc. Thereby ill does not occur and good happens. Prosperity mounts.

Advantage of Tap
We do not distract
We become powerful
Nature bends towards us.
If we do not curse, energy is not released. Based on how successfully we behave under pressure of penance, we get next birth of a heavenly being. Heavens gets a new good power in form of us. Where we may control rains or minds or look after devotees, playing gods.
Due to nature's balance, as we accumulate pain or healthy pain within us, the surrounding people and Nature tries to make us happy and pride is maintained, is one perspective. But unhealthy and extreme penance can create mind imbalance so Lord Krishna advises to avoid extreme penance and adopt healthy penance ( as told by Shastras to us)
What the tapasvis says, happens, thereby Tap enhances Godhood in us. And we are expected not to misuse the Godhood, once activated due to penance.

Advantage of Daan
Act of giving reduces intensity of bad times. The punishment matrix, when comes upon us, programs the surrounding people to harass us. Consequently they are delighted in harassing us. However the act of giving generates good will, thereby spoiling the command of Punishment matrix. That matrix is weakened. So when bad times comes , keep on donating. Donate sugar to ants, or grains to piegeon or sweets and chocolates to small children. Everyone likes good and sweet words. Then why scarcity of good words and praisings. If you have nothing, donate words of compliment. Just give the best, you can to this Nature. Yes, backfire can come, but we should not give up fighting, says Lord Krishna in Gita. Act of Giving is something, we should do eternally, not only on earth, but also in the afterlife.